Pressure Reducing and Relief Valve

ABSTRACT

A pressure regulating and pressure relief valve, has a valve body defining an inlet port, outlet port, valve seat and pressure relief opening. A pressure regulating plug is displaced during a first portion of a motion from an open position, which provides a continuous flow path from the inlet port to the outlet port, to a closed position in which the plug is closed against the valve seat to obstruct the continuous flow path. A spring biases the plug to the open position. An actuation surface is exposed to a pressure at the outlet port that displaces the plug against the spring bias toward the closed position. Further displacement of the plug beyond the closed position during a second portion of the motion that is beyond a range of the first portion of the motion, opens a relief flow path from the outlet port through the pressure release opening.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a pressure reducing valve and, in particular,it concerns a pressure reducing valve with an integrated pressurerelease function.

Irrigation Low Pressure Systems (LPS) tubes are delicate and subject torupture on overpressure and pressure surges. To protect them fromdamage, such systems are typically provided with pressure reducingvalves (PRV) which throttle a variable inlet pressure to produce arelatively constant outlet pressure at a desired value.

SUMMARY OF THE EMBODIMENTS

One aspect is a pressure regulating and pressure releasing valve,comprising (a) a valve body defining an inlet port, an outlet port, avalve seat and a pressure release opening; (b) a pressure regulatingplug configured to be displaced during a first portion of a motion froman open position, which provides a continuous flow path from the inletport to the outlet port, to a closed position in which the plug isclosed against the valve seat to obstruct the continuous flow path; (c)a spring configured to bias the plug from the closed position to theopen position, the plug having an actuation surface exposed to apressure at the outlet port such that the pressure at the outlet portdisplaces the plug against the bias of the spring toward the closedposition, wherein further displacement of the plug beyond the closedposition during a second portion of the motion that is beyond a range ofthe first portion of the motion, opens a relief flow path from theoutlet port through the pressure release opening to an area external tothe valve body.

In some embodiments, the valve body has a central part and a peripheralpart and wherein the valve seat and the plug are structured such thatthe continuous flow path travels through the peripheral part and atleast a portion of the relief flow path travels through the centralpart. In some embodiments, an outer wall of the plug is radially outwardfrom the valve seat relative to a longitudinal axis running through acentral part of the valve body from the inlet port to the outlet port.In some embodiments, the pressure regulating and pressure releasingvalve further comprises a central relief conduit situated such that therelief flow path passes between a rear wall of the plug and the centralrelief conduit. In some embodiments, the relief flow path runs throughan opening in a side wall of the plug.

In some embodiments, the valve body has a central part and a peripheralpart and wherein the valve seat and the plug are structured such thatthe fluid flow path travels through the central part and the relief flowpath is in the peripheral part of the valve body. In some embodiments,an outer wall of the plug is radially inward from an inner wall of thevalve seat relative to a longitudinal axis running through the centralpart of the valve body from the inlet port to the outlet port.

In some embodiments, the central part of the valve body is inside theplug.

In some embodiments, the peripheral part of the valve body is radiallyoutward from the plug relative to a longitudinal axis running through acentral part of the valve body from the inlet port to the outlet port.

In some embodiments, a forward and inward edge of a sleeve of the plugis situated relative to the valve seat such that the continuous flowfluid does not affect displacement of the plug.

In some embodiments, the continuous flow path is provided from the inletport passing between the valve seat and the plug and continuing to theoutlet port.

In some embodiments, the actuation surface comprises a flange at a rearof the plug.

In some embodiments, the plug is displaced linearly relative to thevalve seat during the motion.

In some embodiments, the spring and plug are configured such that whenpressure at the outlet port drops below a set point, the plug is openedby the spring and the continuous flow path is restored so as to recoverpressure at the outlet port.

In some embodiments, the valve body has a central part and a peripheralpart and the valve seat and the plug are structured such that one of thefollowing is true: (i) the fluid flow path travels through theperipheral part and at least a portion of the relief flow path travelsthrough the central part, (ii) the fluid flow path travels through thecentral part and the relief flow path is in the peripheral part of thevalve body.

In some embodiments, a sleeve of the plug is long enough that thefurther displacement of the plug beyond the closed position during thesecond portion of the motion begins to open the relief flow path onlyafter the closed position in which the plug is closed against the valveseat, wherein a length of the sleeve of the plug beyond a thresholdlength of the sleeve corresponds to a range of positions in which theplug has closed against the valve seat without the relief flow pathhaving opened.

In some embodiments, the further displacement of the plug beyond theclosed position during the second portion of the motion begins to openthe relief flow path just when the plug is closed against the valveseat.

Another aspect is a pressure regulating and pressure relief valve,comprising (a) a valve body defining an inlet port, an outlet port, avalve seat and a pressure relief opening; (b) a pressure regulating plugconfigured to be displaced during a first portion of a motion from anopen position, which provides a continuous flow path from the inlet portto the outlet port, to a closed position in which the plug is closedagainst the valve seat to obstruct the continuous flow path; (c) aspring configured to bias the plug from the closed position to the openposition, the plug having an actuation surface exposed to a pressure atthe outlet port such that the pressure at the outlet port displaces theplug against the bias of the spring toward the closed position, whereinfurther displacement of the plug beyond the closed position during asecond portion of the motion that is beyond a range of the first portionof the motion, opens a relief flow path from the outlet port through thepressure release opening to an area external to the valve body, whereinthe valve body has a central part and a peripheral part and wherein thevalve seat and the plug are structured such that the continuous flowpath travels through the peripheral part and at least a portion of therelief flow path travels through the central part, wherein a forward andinward edge of the plug is situated relative to the valve seat such thatthe continuous flow fluid does not affect displacement of the plug.

A still other aspect is a pressure regulating and pressure releasingvalve, comprising (a) a valve body defining an inlet port, an outletport, a valve seat and a pressure release opening; (b) a pressureregulating plug configured to be displaced during a first portion of amotion from an open position, which provides a continuous flow path fromthe inlet port to the outlet port, to a closed position in which theplug is closed against the valve seat to obstruct the continuous flowpath; (c) a spring configured to bias the plug from the closed positionto the open position, the plug having an actuation surface exposed to apressure at the outlet port such that the pressure at the outlet portdisplaces the plug against the bias of the spring toward the closedposition, wherein further displacement of the plug during a secondportion of the motion opens a relief flow path from the outlet portthrough the pressure release opening to an area external to the valvebody and wherein a sleeve of the plug is short enough that the furtherdisplacement opens the relief flow path prior to the closing of the plugagainst the valve seat such that the first portion and the secondportion of the motion overlap, wherein a diminution of the length of thesleeve less than the threshold length corresponds to a range ofpositions in which the relief flow path opens without the plug havingclosed against the valve seat.

These and other features, aspects and advantages of the invention willbecome better understood with reference to the following drawings,descriptions and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1A is a sectional view of a valve that has a fluid flow pathrunning through the central part of the valve body in an open positionwhile the relief port is closed, in accordance with an embodiment of theinvention;

FIG. 1B is a sectional view of the valve of FIG. 1A valve that has afluid flow path running through the central part of the valve body withthe plug partially displaced and the relief port remains closed, inaccordance with an embodiment of the invention;

FIG. 1C is a sectional view of a valve that has a fluid flow pathrunning through the central part of the valve body in a closed positionand the relief port still remains closed, in accordance with anembodiment of the invention;

FIG. 1D is a sectional view of the valve of a valve that has a fluidflow path running through the central part of the valve body with theplug fully displaced beyond the closed position and the relief port isfully open, in accordance with an embodiment of the invention;

FIG. 2A is a sectional view of a valve that has a fluid flow pathrunning through the peripheral part of the valve body in an openposition and the relief port in closed position, in accordance with anembodiment of the invention;

FIG. 2B is a sectional view of a valve that has a fluid flow pathrunning through the peripheral part of the valve body with the plugpartially displaced and the relief port in closed position, inaccordance with an embodiment of the invention;

FIG. 2C is a sectional view of a valve that has a fluid flow pathrunning through the peripheral part of the valve body in a closedposition and the relief port in closed position, in accordance with anembodiment of the invention;

FIG. 2D is a sectional view of a valve that has a fluid flow pathrunning through the peripheral part of the valve body with the plugfully displaced beyond the closed position and the relief port in fullyopen position, in accordance with an embodiment of the invention;

FIG. 3A is a sectional view of a valve that has a fluid flow pathrunning through the peripheral part of the valve body in open positionand the relief port in closed position, in accordance with an embodimentof the invention;

FIG. 3B is a sectional view of a valve that has a fluid flow pathrunning through the peripheral part of the valve body with the plugpartially displaced and the relief port in closed position, inaccordance with an embodiment of the invention;

FIG. 3C is a sectional view of a valve that has a fluid flow pathrunning through the peripheral part of the valve body in a closedposition and the relief port in closed position, in accordance with anembodiment of the invention;

FIG. 3D is a sectional view of a valve that has a fluid flow pathrunning through the peripheral part of the valve body with the plugfully displaced beyond the closed position and the relief port in fullyopen position, in accordance with an embodiment of the invention;

FIG. 3E is a sectional view taken along line B-B of FIG. 3B, inaccordance with an embodiment of the invention;

FIG. 4 is a sectional view similar to FIG. 1B except that the sleeve ofthe plug has been lengthened, in accordance with an embodiment of theinvention; and

FIG. 5 is a schematic view similar to FIG. 1B except that the sleeve ofthe plug has been shortened, in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description is of the best currently contemplatedmodes of carrying out the invention. The description is not to be takenin a limiting sense, but is made merely for the purpose of illustratingthe general principles of the invention, since the scope of theinvention is best defined by the appended claims.

As an additional precaution, low pressure irrigation systems may beprovided with a pressure relief valve which opens in the case of excesspressure in the line to vent the excess pressure to the atmosphere.Instead of the pressure relief valve being an additional systemcomponent which would add cost and involve additional installation andmaintenance overheads to the system, in certain embodiments a singlevalve functions as a pressure regulation valve and a pressure reliefvalve, in one valve body.

Additionally, instead of starting to operate the pressure relieffunction only when the pressure peaks above a preset level, andsuffering from a relatively slow response time, the valve, in certainembodiments, prevents a pressure surge and buildup prior to developmentof the pressure surge and buildup on the downstream system. The valveties the relief opening move to the pressure reducing move, anticipatingand eliminating the potential downstream pressure rise. The relief portis configured to open on the same pressure regulation/reduction move. Incontrast, existing pressure reduction valves react to remedy thedownstream pressure only after the valve senses the pressure rise overthe set points.

The principles and operation of a Pressure Reducing and Relief Valveaccording to the invention may be better understood with reference tothe drawings and the accompanying description.

As shown in FIG. 1A through FIG. 3E, a pressure reducing and pressurereleasing valve 10 comprises a valve body 100 defining an inlet port Aand an outlet port C, a valve seat 110 and a pressure release opening Dalso called the pressure relief port D.

Valve 10 also comprises a pressure regulating plug 140 configured to bedisplaced during a first portion of a motion from an open position,which provides a continuous flow path from the inlet port A to theoutlet port C (by for example passing between the valve seat 110 andplug 140), to a closed position in which the plug 140 is closed againstthe valve seat 110 to obstruct the continuous flow path. During thefirst portion of the motion the closed position is reached when plug 140is displaced enough to contact valve seat 110, thereby cutting off thecontinuous flow path (of fluid such as water). The displacement of plug140 may be linear relative to valve seat 110 during the first part (andsecond part) of the motion.

Valve 10 further comprises a spring 160 configured to bias the plug 140from the closed position to the open position. Plug 140 typically has anactuation surface 150 exposed to a pressure at the outlet port C suchthat the pressure at the outlet port C displaces the plug 140 againstthe bias of the spring 160 toward the closed position. Actuation surface150 may be a flange at a rear of plug 140.

As seen for example in FIG. 1B, valve seat 110 has a cylindrical portionand sleeve 143 of plug 140 also has a cylindrical portion. Thecylindrical portion of plug 140 moves telescopically in overlap with thecylindrical portion of valve seat 110 during a second portion of themotion.

As shown in FIG. 1D (and FIG. 2D and FIG. 3D), further displacement ofplug 140 beyond the closed position during a second portion of themotion that is beyond a range of the first portion of the motion, opensa relief flow path from the outlet port C through the pressure releaseopening D to an area external to the valve body 100.

FIG. 1A through FIG. 1D depicts one particular configuration of valvebody 100. In this configuration, valve body 100 has a central part 102and a peripheral part 104. Valve seat 110 and plug 140 are structuredsuch that the fluid flow path travels through the central part 102 ofvalve body 100 and the relief flow path is in the peripheral part 104 ofthe valve body 100. An outer wall of plug 140 may be radially inwardfrom an inner wall (throat) of the valve seat 110 (relative to alongitudinal axis running through the central part of the valve bodyfrom the inlet port to the outlet port).

FIG. 2A through FIG. 2D depicts another configuration of valve body 100in which the valve seat 110 and the plug 140 are structured such thatthe continuous flow path (of fluid such as water) travels through theperipheral part 104 and at least a portion of the relief flow pathtravels through the central part 102. An outer wall 141, for example anouter side wall 141, of plug 140 may be radially outward from valve seat110. Valve body 100 further comprises a central relief conduit 103situated such that the relief flow path passes between a rear wall ofthe plug and the central relief conduit 103.

FIG. 3A through FIG. 3E depicts another configuration of valve body 100in which the valve seat 110 and the plug 140 are structured such thatthe continuous flow path travels through the peripheral part 104 and atleast a portion of the relief flow path travels through the central part102 (as in FIGS. 2A-2D). An outer wall of the plug 14 may be radiallyoutward from the valve seat 110. In this version shown in FIGS. 3A-3E,however, the relief flow path runs through an opening in a side wall 141of plug 140 rather than alongside the rear wall 150 of plug 140. In oneimplementation, the relief flow path travels through relief windows 135in the central part 102 of valve body 100 to reach the relief port D atwhich pressure is P3 (atmospheric pressure) (FIG. 3B).

In general, valve body 100 has a central part 102 and a peripheral part104 and the valve seat 110 and plug 140 are structured such that one ofthe following is true: (i) the fluid flow path travels through theperipheral part 104 of valve body 100 and at least a portion of therelief flow path travels through central part 102 of valve body 100 or(ii) the fluid flow path travels through central part 102 of valve body100 and the relief flow path is in the peripheral part 104 of valve body100.

In accordance with certain embodiments, for example those shown in FIGS.1-3E, FIGS. 2A-2D and FIGS. 3A-3E, displacement of plug 140 is notaffected by the pressure at the inlet port A. This may be accomplishedby configuring the placement of the edge 143A of the sleeve 143 of plug140 (i.e. the most forward and inward edge of plug 140 or of sleeve 143)relative to throat 116 of valve seat 110 as shown in FIG. 1B (whichremoves the effect of pressure from inlet port A against plug 140) or asshown in FIG. 2B or as shown in FIG. 3B. The forward edge of sleeve 143is situated relative to valve seat 110 such that the continuous flowfluid (from inlet port A) does not affect displacement of the plug 140(or does affect it significantly).

Operation of the Valve Shown in FIG. 1A Through FIG. 1D

Plug 140 may have a flange 150 at the rear of plug 140 that functions asan actuation surface 150. This actuation surface/flange 150 alsofunctions as the Relief closure. Plug 140 and piston 150 move past theclosed position into the throat 116 and open the relief port D as theseal 134 move away from the seat line 133.

Plug 140 is not affected by the upstream pressure P1 and is driven bythe piston 150 pushed by the downstream pressure P2 and plug 140 staysin equilibrium with the preset spring 160 force.

The plug 140 closing position starts at the point at which the edge 143Aof plug 140 engages the seat lip 115.

The opening of the relief port D starts as the piston seal 134 move awayfrom the relief seat line 133.

To avoid plug 140 getting stuck when it meets valve seat 110, the fitbetween them cannot be too tight. One option is leaving a minimalclearance. A further option is to have, besides plug seal 119, anadditional seal (not shown) similar to the O-ring plug seal 119. Thisadditional seal may be situated between plug 140 and throat 116 of valveseat 110 in order to seal the space between plug 140 and throat 116 ofvalve seat 110. This is relevant beginning in the closed position ofFIG. 1C and continuing after plug 140 is displaced further as shown inFIG. 1D. Such an additional seal would be as an alternative to relyingon leaving the minimal clearance between plug 140 and throat 116 tominimize leakage of fluid. Use of the additional seal would be a designconsideration that depends on whether one considers the minimal leakage(resulting from leaving the minimal clearance without the additionalseal) to be acceptable.

As the downstream pressure P2 rises, piston's 150 force prevails overthe force of the spring 160 and plug 140 moves to close, therebyreducing the downstream pressure P2.

If the downstream pressure P2 drops beyond the set point, the spring 160prevails and the valve plug 140 opens thereby recovering the downstreampressure P2. Spring 160 and plug 140 are configured such that whenpressure at the outlet port C drops below a set point, plug 140 isopened by spring 160 and the continuous flow path is restored so as torecover pressure P2 at the outlet port C.

The following parts of valve body 100 are labeled in FIGS. 1A-1D:

A Inlet port

B Throttled downstream pressure zone

C Outlet port

D Relief port

P1 Upstream pressure

P2 Downstream pressure

P3 Relief pressure (Atmosphere)

100 Pressure Reducing-Relief Valve Body

110 Seat segment

111 Rib

112 Rib

115 Seat lip

116 Seat throat

117 Seat segment flange

118 Stop rib

119 Plug seal

120 Inlet body segment

121 Seal

125 Inlet connection grooved

126 Inlet segment flange

130 Outlet body segment

131 Outlet back wall

132 Seal

133 Relief seat

134 Relief seal

135 Outlet connection grooved

136 Relief connection grooved

137 Outlet segment flange

138 Outlet segment leg

140 Throttling plug

150 Piston

155 Stop rib

160 Spring

170 Bolt-Washer-Nut

Operation of the Valve Shown in FIGS. 2A-2D

Plug 140 may have a rear wall 150 at the rear of plug 140 that functionsas an actuation surface 150. This actuation surface 150 also functionsas the Relief closure. Plug 140 including its rear wall 150 move pastthe closed position so as to enclose seat 110 and open the relief port Das the seal 134 move away from the seat line 133.

Plug 140 is not affected by the upstream pressure P1 and is driven bythe actuation surface/rear wall 150 pushed by the downstream pressure P2and plug 140 stays in equilibrium with the preset spring 160 force.

The plug 140 closing position starts at the point at which the lip 145of plug 140 engages the seat lip 115.

The opening of the relief port D starts as the piston seal 134 move awayfrom the relief seat line 133.

As the downstream pressure P2 rises, piston's 150 force prevails overthe force of the spring 160 and plug 140 moves to close, therebyreducing the downstream pressure P2.

If the downstream pressure P2 drops beyond the set point, the spring 160prevails and the valve plug 140 opens thereby recovering the downstreampressure P2. Spring 160 and plug 140 are configured such that whenpressure at the outlet port C drops below a set point, plug 140 isopened by spring 160 and the continuous flow path (of fluid such aswater) is restored so as to recover pressure P2 at the outlet port C.

Operation of the Valve Shown in FIG. 3A-3E

As the lip 145 of plug 140 of the valve moves past the main valve flowclosing position, it opens the relief flow windows 135 to the collectionchannel 136 and to the drain port D to P3 (atmosphere).

The plug 140 is unaffected by upstream pressure P1 and is driven by thecross-section of rear flange 150 of plug 140 affected by the downstreampressure P2 and plug 140 stays in equilibrium with the preset spring 160force.

The closing position of pressure reducing plug 140 starts as the pluglip 145 engages the seat lip 115. At the same instance the relief flowstarts as the relief window tip 133 move away from the seal 134.

As the downstream pressure P2 rises, the force of plug 140 (which isequal to the cross section of piston 150 times P2) prevails over theforce of the spring 160 and the plug 140 moves to close, therebyreducing the downstream pressure P2.

If the downstream pressure P2 drops beyond the set point, the force ofspring 160 prevails over the force of plug 140 and plug 140 is reopenedby the force of the spring 160, thereby recovering the downstream P2.

The following parts of valve body 100 ae labeled in FIGS. 3A-3E

A Inlet port

B Throttled downstream pressure zone

C Outlet port

D Relief port

P1 Upstream pressure

P2 Downstream pressure

P3 Relief pressure (Atmosphere)

100 Valve Body

105 Valve Body flange

106 Outlet connection groove

110 Inlet flow diffuser

111 Ribs

115 Seat lip

118 Stop surface

119 Plug seal

120 Inlet body segment

121 Seal

125 Inlet connection grooved

126 Inlet segment flange

130 Relief segment

133 Relief widow tip

134 Relief seals

135 Relief widows

136 Relief collection Channel

137 Relief collection casing

140 Throttling plug

145 Plug lip

155 Stop ribs

160 Spring

170 Bolt-Washer-Nut

In FIGS. 1A-FIG. 3E, the length of sleeve 143, i.e. side wall 141 ofplug 140, is such that in some embodiments plug 140 closes at or aroundthe same time that the relief flow along relief flow path to relief portD opens. The further displacement of the plug 140 during the secondportion of the motion begins to open the relief flow path just when plug140 is closed against valve seat 110.

In other versions of valve body 100, sleeve 143 of plug 140 may belengthened or shortened (in proportion to the other parts of valve body100) compared to FIGS. 1A-3E. For example, if sleeve 143 is lengthenedrelative to FIG. 1A to FIG. 3E, for example as shown in FIG. 4, the flowalong relief flow path to relief port D opens only after the closing ofplug 140. For example, in the context of the embodiment shown in FIGS.1A-1D this is only after plug 140 enters the throat (i.e. inner wall) ofvalve seat 110 (in one non-limiting example after plug 140 enters valveseat 110 and has traveled 3% of its expected travel inside valve seat110). Accordingly, in that case, plug 140 is long enough that thefurther displacement of plug 140 beyond the closed position during thesecond portion of the motion begins to open the relief flow path onlyafter plug 140 is closed against valve seat 110. In some embodiments, alength of the sleeve 143 of plug 140 beyond a threshold length of sleeve143 (wherein the threshold length of sleeve 143 is the length of sleeve143 such that the relief flow path opening would occur simultaneouslywith the closing of plug 140 against valve seat 110) corresponds to arange of positions in which plug 140 has closed against valve seat 110and the opening of the relief flow path has not yet occurred.

On the other hand, as shown in FIG. 5, if sleeve 143 of plug 140 isshortened relative to FIGS. 1A to FIG. 3E, the flow along relief flowpath to relief port D opens prior to the closing of plug 140 (as anon-limiting example, prior to the last 5% of the traveling of plug 140before its closing). In that case, the first portion of the motion ordisplacement of plug 140 and the second portion of the motion of plug140 overlap. Plug 140 is short enough that its further displacementduring the second portion of the motion opens the relief flow path priorto the closing of plug 140 against valve seat 110.

In some embodiments, the magnitude that the length of the sleeve 143 isshorter than a threshold length of the sleeve 143 (wherein the thresholdlength of sleeve 143 is the length of sleeve 143 such that the reliefflow path opening would occur simultaneously with the closing of plug140 against valve seat 110) corresponds to a range of positions in whichthe relief flow path is open without plug 140 having closed againstvalve seat 110.

It will be appreciated that the above descriptions are intended only toserve as examples, and that many other embodiments are possible withinthe scope of the present invention as defined in the appended claims.

What is claimed is:
 1. A pressure regulating and pressure releasingvalve, comprising: (a) a valve body defining an inlet port, an outletport, a valve seat and a pressure release opening; (b) a pressureregulating plug configured to be displaced during a first portion of amotion from an open position, which provides a continuous flow path fromthe inlet port to the outlet port, to a closed position in which theplug is closed against the valve seat to obstruct the continuous flowpath; (c) a spring configured to bias the plug from the closed positionto the open position, the plug having an actuation surface exposed to apressure at the outlet port such that the pressure at the outlet portdisplaces the plug against the bias of the spring toward the closedposition, wherein further displacement of the plug beyond the closedposition during a second portion of the motion that is beyond a range ofthe first portion of the motion, opens a relief flow path from theoutlet port through the pressure release opening to an area external tothe valve body, wherein the valve body has a central part and aperipheral part and wherein the valve seat and the plug are structuredsuch that the continuous flow path travels through the peripheral partand at least a portion of the relief flow path travels through thecentral part, wherein the relief flow path runs through an opening in aside wall of the plug, and wherein the central part of the valve body isinside the plug in the open position and in the closed position.
 2. Thevalve of claim 1, wherein an outer wall of the plug is radially outwardfrom the valve seat relative to a longitudinal axis running through thecentral part of the valve body from the inlet port to the outlet port.3. The valve of claim 1, wherein a peripheral part of the valve body isradially outward from the plug relative to a longitudinal axis runningthrough the central part of the valve body from the inlet port to theoutlet port.
 4. The valve of claim 1, wherein a forward and inward edgeof a sleeve of the plug is situated relative to the valve seat such thatan upstream pressure does not affect displacement of the plug.
 5. Thevalve of claim 1, wherein the continuous flow path is provided from theinlet port passing between the valve seat and the plug and continuing tothe outlet port.
 6. The valve of claim 1, wherein the plug is displacedlinearly relative to the valve seat during the motion.
 7. The valve ofclaim 1, wherein the spring and plug are configured such that whenpressure at the outlet port drops below a set point, the plug is openedby the spring and the continuous flow path is restored so as to recoverpressure at the outlet port.
 8. The valve of claim 1, wherein a sleeveof the plug is long enough that the further displacement of the plugbeyond the closed position during the second portion of the motionbegins to open the relief flow path only after the closed position inwhich the plug is closed against the valve seat, wherein a length of thesleeve of the plug beyond a threshold length of the sleeve correspondsto a range of positions in which the plug has closed against the valveseat without the relief flow path having opened.
 9. The valve of claim1, wherein the further displacement of the plug beyond the closedposition during the second portion of the motion begins to open therelief flow path just when the plug is closed against the valve seat.10. The valve of claim 1, wherein the further displacement of the plugbeyond the closed position opens the relief flow path from the outletport through the pressure release opening to an area external to thevalve body while flow from the inlet port remains obstructed.
 11. Thevalve of claim 1, wherein the actuation surface is exposed to thepressure at the outlet port such that the pressure at the outlet portdisplaces the plug against the bias of the spring toward the closedposition as a continuous function of the outlet pressure, therebyachieving outlet pressure regulation.
 12. A pressure regulating andpressure relief valve, comprising: (a) a valve body defining an inletport, an outlet port, a valve seat and a pressure relief opening; (b) apressure regulating plug configured to be displaced during a firstportion of a motion from an open position, which provides a continuousflow path from the inlet port to the outlet port, to a closed positionin which the plug is closed against the valve seat to obstruct thecontinuous flow path, wherein a central part of the valve body is insidethe plug in the open position and in the closed position; (c) a springconfigured to bias the plug from the closed position to the openposition, the plug having an actuation surface exposed to a pressure atthe outlet port such that the pressure at the outlet port displaces theplug against the bias of the spring toward the closed position, whereinfurther displacement of the plug beyond the closed position during asecond portion of the motion that is beyond a range of the first portionof the motion, opens a relief flow path from the outlet port through thepressure release opening to an area external to the valve body, whereinthe valve body has the central part and a peripheral part and whereinthe valve seat and the plug are structured such that the continuous flowpath travels through the peripheral part and at least a portion of therelief flow path travels through the central part and wherein the reliefflow path runs through an opening in a side wall of the plug, wherein aforward and inward edge of the plug is situated relative to the valveseat such that an upstream pressure does not affect displacement of theplug.
 13. The valve of claim 12, wherein a peripheral part of the valvebody is radially outward from the plug relative to a longitudinal axisrunning through the central part of the valve body from the inlet portto the outlet port.
 14. A pressure regulating and pressure releasingvalve, comprising: (a) a valve body defining an inlet port, an outletport, a valve seat and a pressure release opening; (b) a pressureregulating plug configured to be displaced during a first portion of amotion from an open position, which provides a continuous flow path fromthe inlet port to the outlet port, to a closed position in which theplug is closed against the valve seat to obstruct the continuous flowpath, wherein the valve body has a central part and a peripheral partand wherein the peripheral part of the valve body is radially outwardfrom the plug relative to a longitudinal axis running through a centralpart of the valve body from the inlet port to the outlet port; (c) aspring configured to bias the plug from the closed position to the openposition, the plug having an actuation surface exposed to a pressure atthe outlet port such that the pressure at the outlet port displaces theplug against the bias of the spring toward the closed position, whereinfurther displacement of the plug beyond the closed position during asecond portion of the motion that is beyond a range of the first portionof the motion, opens a relief flow path from the outlet port through thepressure release opening to an area external to the valve body, whereinthe valve seat and the plug are structured such that the continuous flowpath travels through the peripheral part and at least a portion of therelief flow path travels through the central part and wherein the reliefflow path runs through an opening in a side wall of the plug.
 15. Thevalve of claim 14, wherein the continuous flow path is provided from theinlet port passing between the valve seat and the plug and continuing tothe outlet port.
 16. The valve of claim 14, wherein the plug isdisplaced linearly relative to the valve seat during the motion.
 17. Thevalve of claim 14, wherein the spring and plug are configured such thatwhen pressure at the outlet port drops below a set point, the plug isopened by the spring and the continuous flow path is restored so as torecover pressure at the outlet port.